Popular fiction is not, necessarily, light. Tristan Sadler, narrator of The Absolutist, travels to Norwich just after the First World War. He is reading White Fang by Jack London, and he meets on the train an Agatha Christie-like crime novelist who cheerfully describes the crisp justice she dishes out. John Boyne too is a popular novelist (best known for The Boy in the Striped Pyjamas), but neither London’s adrenalin-stoked adventure nor Christie’s neat parcels of motive and retribution are his models here.